The House of Saud, and particularly Crown Prince Mohammed bin Salman (MBS), has been under fire for weeks after U.S.-based Saudi journalist Jamal Khashoggi was tortured and killed inside the Saudi consulate in Istanbul. On Tuesday, Trump continued his long defense of the Saudis by virtually shrugging the whole thing off.

King Salman and Crown Prince Mohammad bin Salman vigorously deny any knowledge of the planning or execution of the murder of Mr. Khashoggi. Our intelligence agencies continue to assess all information, but it could very well be that the Crown Prince had knowledge of this tragic event — maybe he did and maybe he didn't!

That being said, we may never know all of the facts surrounding the murder of Mr. Jamal Khashoggi. In any case, our relationship is with the Kingdom of Saudi Arabia. They have been a great ally ... [Trump]

This is extraordinary. It's also not the first time Trump has expressed willful oblivion toward the Saudi regime's role here. Pressed this weekend by Fox News' Chris Wallace on whether MBS lied to his face about involvement in Khashoggi's murder — the CIA reportedly says he did — Trump equivocated.

"I don't know. You know, who can really know?" he said. Wallace pressed on: "But what if he's lying? Do you just live with it because you need him? … If Congress were to move to either try to cut off any U.S. involvement in the war in Yemen or to block any arms sales you won't go along with it?"

Trump's response was the usual serpentine tangle, but it wound toward "yes." The U.S. has "an ally" in Saudi Arabia, he said, "and I want to stick with an ally that in many ways has been very good." Even if MBS lied about Khashoggi, even if Congress sought to end American support for the disastrous Saudi-led intervention on Yemen or cut off U.S. arms sales to Riyadh, Trump would keep America tied to the House of Saud.

Why?

Some of this dynamic, no doubt, is attributable to the president's confidence in his own ability to develop useful personal relationships with foreign leaders. Trump seems to envision the world stage as the hospitality or development business scaled up, so his friendship can reliably purchase mutual backscratching. This attitude is a mixed blessing, as it pushes the administration toward needed diplomatic endeavors — as with North Korea — but can also undercut negotiations by equipping Trump with a simplistic approach. (However much he "fell in love," North Korean leader Kim Jong Un isn't going to give up his nuclear arsenal over friendly feelings.)

But the United States' strangely close relationship with Saudi Arabia is not of Trump's creation. We've been committed to Riyadh for years, maintaining the alliance through administrations from both major parties. It is not difficult to imagine, say, former President Barack Obama — originator of U.S. backing for Saudi intervention in Yemen and Riyadh's favorite arms dealer — making essentially the same move in response to MBS's lies.

I have no illusions that the United States will only deal with "nice" nations that love liberty, justice, and democracy. In fact, as messy as they can be, I think trade and diplomacy stand the strongest chance of peacefully moving oppressive and otherwise unsavory countries toward freedom and normalcy. But that realism does not mean that cultivating this close alliance with Saudi Arabia is defensible. Khashoggi's death has forced a conversation we should have been having anyway, a conversation about how staying allied with the Saudi regime violates the values we claim without benefiting our national interest. This is fundamentally a partnership with just another murderous and oppressive Mideast dictatorship that undermines regional stability and makes us look like hypocrites in the process.

Sen. Rand Paul (R-Ky.) is among the loudest voices recognizing this multifaceted foreign policy failure and pushing Trump to serve MBS a punishment he may actually heed: ending U.S. weapons deals with Riyadh. Paul made this case at length in a speech at The American Conservative's recent foreign policy conference, highlighting both the Saudi intervention's devastating humanitarian consequences in Yemen and the Saudi regime's record of radicalization and destabilization that undermines U.S. security.

"My main objection to this whole thing is that the war in Yemen is a tragedy, like most wars, but it's a particular tragedy because they're one of the poorest countries on the planet," Paul said, noting the famine conditions and cholera epidemic the Saudi intervention has produced. These are "things that don't happen in the modern world, really, anymore," he continued, "and so I think it is something that we should not be participating in."

But Yemen is not the Saudi regime's only victim. "If you ask me who's the worst at spreading hatred and trying to engender terrorism around the world, it's Saudi Arabia hands down," Paul argued, listing examples of Saudi support for extremism. In Yemen specifically, the Saudi fight has fostered power vacuums in which al Qaeda in the Arabian Peninsula (AQAP), which aims to conduct 9/11-style attacks in the West, has flourished.

Recognizing this detriment to U.S. interests, again, does not mean initiating conflict or cutting off all contact with Saudi Arabia. It means not linking America to this gruesome government. "I'm very unhappy with Saudi Arabia. I don't like what they're doing, spreading messages throughout the world," Paul said on this point. "But I wouldn't have an embargo of Saudi Arabia. I'm not for not trading with them. … Let's just don't reward them with weapons."

Not rewarding Riyadh with weapons is a pretty simple ask — an ask with which Trump should be able and eager to comply. What's stopping him?